The Beaver Dam Eye Study was designed to determine the prevalence and severity of cataract, age-related maculopathy, glaucoma and visual impairment. About one quarter of the 5,189 persons aged 43 to 84 who participated in the study formed sibships of size two or larger. Sibling correlations were calculated for numerous traits for which these persons were scored on ophthalmologic examination, and then those traits for which there were significant sibling correlations were subjected to segregation analysis. Indications of autosomal recessive inheritance were found for objective quantitative scores related to three particular conditions: (1) age-related maculopathy, measured on a 15-step scale and adjusted for age by quadratic regression; (2) nuclear sclerosis, measured on an 11-step scale, similarly adjusted for age; and (3) cortical cataract, measured as the percent area involved with cortical opacities, adjusted for both age and sex. A linkage study is in progress with a view to confirming the existence of one or more of these major genes for visual impairment and determining the relevant genomic location(s). [unreadable]